Stable isotope tracers have become invaluable tools with which to investigate human metabolism. This laboratory has been involved in the application and development of stable isotope tracer methods for 20 years. New kinetic models and analytical approaches have been developed in this lab to investigate aspects of glucose, fat and protein metabolism. A major goal of this core laboratory is to make available mass spectrometry analysis for all Pepper OAlC projects. More generally, we will assist investigators in all aspects of tracer methodology necessary to use this approach to study metabolism in elderly individuals. We have all the equipment necessary to perform stable isotope enrichment measurements, including six quadrupole gas chromatograph mass spectrometers (GCMS), a gas chromatography-combustion-isotope ratio mass spectrometer (GC/C/I RMS), an isotope ratio mass spectrometer (IRMS) interfaced to an elemental analyzer, and a liquid chromatograph/quadrupole mass spectrometer (LCQMS). We also have expertise in experimental design, performance and analysis of tracer studies, and in mathematical modeling. We initially propose three novel developmental projects that will enhance our future investigations of amino acid and fatty acid kinetics. This core will also provide analysis needed to quantify tissue lipid content using magnetic resonance spectroscopy, and in vivo tissue ATP production using nuclear magnetic resonance. We will also provide the equipment to measure tissue blood perfusion using the microbubble technique, and also to measure the in vitro mitochondrial oxidative capacity of muscle samples from human subjects. Body composition determination by DEXA is also available. Finally, we are actively involved in training and education. Every year we offer an intensive, one-week formal course on tracer methodology to interested investigators. We also have a PhD program on human metabolism/nutrition, and an active research fellow program that includes one formal meeting per week, in addition to formal training.